Cryptochrome-mediated hypocotyl phototropism was regulated antagonistically by gibberellic acid and sucrose in Arabidopsis

Both phototropins(phot1 and phot2)and cryptochromes(cry1 and cry2)were proven as the Arabidopsis thaliana blue light receptors.Phototropins predominately function in photomovement,and crypto-chromes play a role in photomorphogenesis.Although cryptochromes have been proposed to serve as positive modulators of phototropic responses,the underlying mechanism remains unknown.Here,we report that depleting sucrose from the medium or adding gibberellic acids(GAs)can partially restore the defects in phototropic curvature of the phot1 phot2 double mutants under high-intensity blue light;this restoration does not occur in phott phot2 cry1 cry2 quadruple mutants and nph3(nonphototropic bypocotyl 3)mu-tants which were impaired phototropic response in sucrose-containing medium.These results indicate that GAS and sucrose antgonistically regulate hypocotyl phototropism in a cryptochromes dependent manner,butit showed a crosstalk with phototropin signaling on NPH3.Furthermore,cryptochromes activation by blue light inhibit GAS synthesis,thus stabilizing DELLAS to block hypocotyl growth,which result in the higher GAs content in the shade side than the lit side of hypocotyl to support the asymmetric growth of hypocotyl.Through modulationof the abundance of DELLAS by sucrose depletion or added GAs,it revealed that cryptochromes have a function in mediating phototropic curvature.